Marine System Analysis Group

Hydrogen sulfide, H₂S, is a chemical compound that is easily recognized by its smell of rotten eggs. The substance is toxic for most organisms and is formed in anoxic environments where sulphur is present. The Baltic Sea and the Byfjord is two examples of where hydrogen sulfide is common. In the Byfjord, hydrogen sulfide is present at relatively shallow depths, just beneath the sill level due to anoxic conditions. Every second to fifth year new saline and oxygen rich water manages to flow over the Sunningen sill and down into the deep water of the Byfjord, at least partly renewing some of the resident water. At these events, hydrogen sulfide is oxidized thus sharply reducing its concentration. However, the oxygen concentrations also decrease. When all of the oxygen is consumed, the build-up of hydrogen sulfide starts again. The BOX-project aims at mimicing this natural mechanism of water renewal in an artificial way, thus improving the oxygen conditions and remove the hydrogen sulfide permanently.

In the graph the total amount of hydrogen sulfide integrated over depth in the Byfjord is shown as metric tonnes. The figure is updated at every new measurement of hydrogen sulfide, typically once or twice per month.

Metric tonnes of hydrogen sulfide in the Byfjord (integrated over depth). Note: Interpolating has been done, so these numbers should only be taken as indicative. Original data from the BOX-project and Bohuskustens Vattenvårdsförbund. Click on the image for a larger version.